"Here we go," said Art, stationing himself at a tiny port in the rear of his flier. "Zoom down over that first signal--as soon as you've passed over it, kick her up again at a slight angle." Horne obeyed. They passed the target; nothing happened. He was beginning to wonder what Art was waiting for, when a half mile past the smoke column, Art fired. The resulting concussion surprised even Art. He felt the ship lurch as it was thrown like a huge projectile high above the city. He grinned as he watched Horne, cursing and fighting until he had the bucking ship under control. [Illustration: _The disintegrator blasted, and hell exploded on the ground._] "Let's take a look," he said, sobering at once. He had an uneasy feeling concerning the way in which the grounded population was taking the shock. But his fears were not realized--the stranded folk nearest the explosion cheered and gave the ancient thumbs-up sign, as they skimmed low above the rooftops. Evidently most of the force of the explosion had expended itself upward. "Get below--here we come again!" shouted Art through an open port. The sun was descending beyond the blue Pacific, but they went on with their work of continually blasting, blasting, far into the night. Clouds of private fliers began to appear from neighboring California and other southwest cities. Art's desperate appeal had had its effect. By midnight, people were beginning to stumble through the string of smoking craters that had been made for them, toward the untouched open fields and groves to the north. By four o'clock, they were stringing out on the many roads and streets which left the city in that direction. Busses and private cars had been summoned, and were picking them up, to scatter them through neighboring cities where they might find accommodations. Art and Horne, bruised and stunned from continual concussion and buffeting, exhausted from lack of sleep, looked at each other. * * * * * "Guess that's it," said Art. "You'll have to keep the men along the trail with their electron rays, to keep those devils from closing in at the edges." They had found that a line of men armed with these short-range weapons, could kill enough of the creatures to keep them from spreading. The electron ray generated enough sheer heat to melt metal, which was necessary to destroy the organisms. "The city should be cleared by noon," Art went on. "I'd advise you to destroy the whole works immediately. I'll leave you one of the disintegrators. But be careful. Make sure all the wounded are out." "Are you leaving already?" asked Horne, surprised. "How come?" "Just heard from Dr. Theller," Art answered wearily. "It seems I'm wanted in Detroit. Same thing is happening there." "No!" gasped Horne. "In Detroit! What do you suppose is the connection?"